The present invention relates to a press roll which serves for treating material in web form, preferably for the removal of water from a fiber web, and which press roll forms a press nip with a mating press roll, and in particular relates to the mounting of a press shell to the press roll.
A press roll is typically used for the treatment of a web, and preferably in the dewatering of a fiber web. The press roll forms a press nip, for example, with a mating roll. The press roll includes a support body which is either stationary or is rotatable along with the roll. There is an endless beltlike, flexible, liquid tight press shell which is disposed around the support body and is supported by it. Axially outward of the support body at at least one end there is a press shell support element in the form of a disk, ring or the like, and that shell support element is rotatable, because the press shell is secured to it to rotate with it.
The press shell has at at least the one end, and preferably at both ends, an edge zone which first extends out over and past the shell support element and is then turned radially inward to be fastened to the axially outwardly facing, face side of the shell support element. The edge zone of the press shell has an annular face side sealing surface which can be pressed by a clamping flange, or the like, against the face side of the shell support element. There are distributed along the edge zone of the press shell a plurality of uniformly distributed axially outwardly projecting tongues which extend toward the axis of the press roll when the edge zone is turned inwardly. The tongues are shaped and spaced so that there is a respective cutout in the press shell between neighboring tongues.
Various centering elements may be disposed on the outwardly facing, face side of the shell support element, and these projecting centering elements extend into the cutouts between the tongues of the shell and position the shell with respect to the shell support element. In particular, the centering elements rest against the bases of the cutouts.
Holding elements are also provided, which may comprise a pin, bolt, or the like, extending out of the outwardly facing, face side of the shell support element. In an alternate embodiment, those holding elements may be defined at the annular clamping flange that clamps the edge zone of the press shell to the face side of the shell support element.
The holding elements and the centering elements are respectively radially so placed that with the tongues supported on the respective holding elements, the centering elements press into the bases of the cutouts and those centering elements tension the press shell as the tongues are tightened by being placed upon the holding elements.
The shell support elements are normally axially outwardly biased from the support body thereby to axially tension the press shell. Means for temporarily pushing the shell support elements axially inwardly against the normal outward bias are provided on the support body, and with the shell support elements pushed axially inwardly, is easier to mount to the press shell on the holding elements. Thereafter, the shell support elements are again permitted to be biased outwardly.
The invention also concerns a method of mounting the press shell on the apparatus described. The press shell is drawn over the support body and over the shell support elements, so that the edge zones are brought to extend beyond the shell support elements and are then turned radially inwardly so that the tongues extend inward and are mounted to the holding elements while the centering elements move into the bases of the cutouts between neighboring tongues. For facilitating the mounting of the press shell, the shell support elements are temporarily moved axially inwardly until the tongues are mounted to the holding elements.
Such a press roll is known from Federal Republic of Germany Published Application DE-OS No. 35 01 635, which is equivalent to U.S. Pat. No. 4,625,376.
For known press rolls, as well as for rolls according to the present invention, there are two different types of construction. In the one type, the support beam, which extends through the surrounding press shell, is stationary. In the other type, the support body is mounted for rotation in a manner similar to the press shell.
With a stationary support body that does not rotate, in the region of the press nip, the flexible belt like press shell slides over the support body in the circumferential region where the support body presses the press shell against the mating roll. A radially movable press shoe over which the press shell slides is preferably provided on the support body for this purpose, in accordance with Federal Republic of Germany Published Application DE-OS No. 33 11 996, which corresponds to U.S Pat. No. 4,555,305. The slide surface of the press shoe is usually concave, generally in accordance with the curvature of the mating roll, so that the press nip has a certain longitudinal length in the direction of travel of the web, i.e., an elongate press nip is formed. The cross-sectional shape of the support body can in this case be of any desired shape, for instance rectangular, tubular or I-shaped.
If the support body is of the type that is mounted for rotation and has the shape of a circular cylindrical roll body, then when the support body presses the press shell against the mating roll, it travels on the inside of the press shell in the region of the press nip.
In known press rolls, as well as of the press roll of the invention, the press shell is always developed liquid tight since the inside of the press shell must be wetted with lubricant, but none of the lubricant should penetrate to the outside from the inside of the press roll. If the lubricant did penetrate to the outside, there is a danger that the web to be treated would be dirtied.
For these reasons, it is also very important that the ends of the press shell be connected in absolutely liquid tight manner to the two press shell support elements, which are mounted rotatably on the support body. Furthermore, it is important that this connection can be both made and opened within a short time, because after a period of operation, it must be expected that the press shell will have to be replaced by a new one. When the press roll is used, for instance, in a paper making machine, it is important that the press shell be replaced in the shortest possible time, in order to reduce the machine standstill time as much as possible.
Furthermore, with the known press shell roll, as well as with the press roll of the invention, the press shell is preferably made of a reinforced and relatively hard plastic, for instance polyurethane. A fabric is preferably provided as reinforcement.
Known measures for liquid-tight attachment of the ends of the press shell to the shell support elements in the known press roll have proven worthwhile in practice. However, difficulties are still at times encountered in attaching a new press shell to the shell support elements within the shortest possible time. For example, during this mounting, it is important to center the ends of the press shell as accurately as possible on the shell support element, since the smooth travel of the press shell in operation depends upon this.